I. Field of the Invention
This invention relates to respiratory gas delivery devices, which are responsive to a patient""s breathing cycle and more particularly for providing oxygen to a patient only during the first portion of inhalation, such that oxygen is delivered to the patient only when it will be admitted to the lungs and not when it will remain in the patient""s air passageways only to be exhaled.
II. Description of the Related Art
Patients with lung diseases frequently need oxygen delivered to their lungs as part of their therapy.
A continuous flow of oxygen to the patient is easily applied such that when the patient inhales there is oxygen available in a mask or cannula. However a continuous flow is not needed, particularly while the patient is exhaling.
Patient mobility is affected by the size of the oxygen bottles, their weight and how long they will last while the patient is carrying their oxygen supply with them. An oxygen economizing device can be used to make the oxygen in the bottle last longer and also reduce the size and weight of the bottle that needs to be transported with the patient for greater mobility.
Some oxygen economizers use electronic sensors and controls to deliver oxygen. This requires batteries, which must be constantly replaced and electronic controls, which may fail.
Some oxygen economizers use dual lumen cannulas, with one lumen for delivery of oxygen to the patient and one lumen for sensing breathing pressures. Dual lumen cannulas cost more and are not as comfortable for the patient.
Oxygen delivery devices have been developed wherein oxygen is supplied to the patient starting when the patient begins to inhale and ending when the patient begins to exhale, thus conserving oxygen. However, this too wastes oxygen as the patient only benefits from the first part of the oxygen inhaled, which goes to the patient""s lungs. The remainder of the inhaled oxygen remains in the air passageways to the lungs and is immediately exhaled, thus wasting oxygen.
At least one oxygen economizer uses a series of pulses of oxygen during the inhalation cycle. The pulse of oxygen is delivered and then a check is made to see if the patient is still inhaling. If he is then another pulse is delivered. This method is irritating for the patient and wastes oxygen as the airways of the patient as well as the lungs receive oxygen.
A device is needed which will provide oxygen during initial inhalation and then reduce or eliminate the amount of oxygen delivered thereafter rather than deliver gas as a series of pulses. The oxygen delivery device should provide either a fixed or adjustable volume of oxygen for a fixed time at a fixed or adjustable flow rate such that patients having different breathing patterns can be treated. The oxygen delivery device should be pneumatic, avoiding batteries and other problems associated with electronic devices. The oxygen delivery device should also be used with a comfortable single lumen cannula.
The invention provides for a diaphragm to detect the commencement of inhalation and a timed application of oxygen such that the first portion of the inhalation in the breathing cycle receives oxygen and the balance of the inhalation cycle receives little or no oxygen.
The invention comprises a breath sensing portion with a sensing diaphragm for detecting a drop in pressure when a patient starts inhaling. The diaphragm moves to reduce the pressure in a gas delivery timer portion wherein a delivery diaphragm is displaced from a gas delivery seat for an adjustable amount of time to provide oxygen to a patient during the first portion of inhalation. The volume and flow rate of oxygen delivered to the patient is regulated by a variable flow rate portion in combination with the gas delivery timer portion. When oxygen begins flowing to the patient, oxygen entering the sensing chamber pushes the sensing diaphragm over a seat leading to the gas delivery timer portion. Oxygen entering the gas delivery timer portion builds up pressure and moves a diaphragm over a seat, cutting off the oxygen supply to the patient after the initial portion of inhalation. In this manner oxygen is delivered to the patient""s lungs and not to his airways, which will be immediately expelled on exhaling.
If oxygen is only delivered during early inspiration, there will be a negative pressure in the cannula again at the end of the gas delivery. It is not desirable to deliver a second pulse, which would likely be only wasted. The invention avoids this phenomenon by providing a low flow xe2x80x9ctail volumexe2x80x9d from a reservoir which creates enough back pressure in the cannula to block out any continued patient effort.
It is an object of the invention to use oxygen efficiently during respiratory therapy.
It is an object of the invention to provide oxygen to a patient only during initial inspiration to avoid filling the airway of the patient with oxygen.
It is an object of the invention to use a pneumatic control device to deliver oxygen to the patient.
It is an object of the invention to provide a selectable preset volume of oxygen to the patient during each breath.
It is an object of the invention to extend the duration of use of each bottle of oxygen.
It is an object of the invention to reduce the size of the bottle of oxygen that a patient needs to transport when mobile.
It is an object of the invention to reduce the weight of the bottle of oxygen that a patient needs to transport when mobile.
It is an object of the invention to avoid multiple pulses of oxygen flowing to the patient.
It is an object of the invention to use a lumen single cannula with the pneumatic oxygen conserving device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.